Conventionally, development of a device including a plurality of electric brake devices individually corresponding to a plurality of wheels, and a braking control device, which controls each of the electric brake devices, has been proceeded as a braking system mounted on a vehicle (refer to Patent Document 1). Each of the electric brake devices configuring such a system includes a motor driven based on command signals from the braking control device and applies braking force in accordance with the current value for the motor to the corresponding wheel.
When the motor provided in each electric brake device continues to be used even if the temperature thereof becomes greater than or equal to a predetermined heatproof temperature, the motor is likely to have abnormalities. In the above described braking system, if any abnormal motor is present in the motors, a motor protection control for protecting the abnormal motor is performed. In the motor protection control, the current value for the abnormal motor, which corresponds to a first wheel (for example, the right front wheel) is rapidly reduced, and another motor (hereinafter, referred to as “normal motor”) that to a second wheel (for example, the left front wheel) positioned opposite to the first wheel in the lateral direction of the vehicle is operated. Thereby, even if the braking force applied to the first wheel is reduced, the braking force applied to the second wheel is not reduced. Therefore, the reduction of the braking force applied to the entire vehicle is limited, and the abnormal motor is appropriately protected.
However, when the above described motor protection control is started, a braking force difference is generated between the braking force of the first wheel and the braking force of the second wheel (hereinafter, referred to as “right-and-left braking force difference”). As a result, the yaw moment of the vehicle becomes great so that the behavior of the vehicle is likely to be unstable. Accordingly, in the above described braking system, if the abnormal motor is present in the case where the running state of the vehicle is stable, the motor protection control is performed. The determination “whether the running state of the vehicle is stable” is performed by determining “whether the sideslip of the vehicle is unlikely to be caused”, for example.